1. Field of the Invention
The present invention relates to the prefabrication of insulating panels used as the structurally stiff and gas impervious insulating wall of cryogenic tanks of the membrane type, in which the cryogenic liquid (LNG, liquid ethylene, nitrogen, oxygen, etc.) is contained by a thin metal liner (membrane) supported by a rigid insulating layer which transmits the hydrostatic and thermal stresses due to the cold liquid to an outer load-bearing vessel structure (inner hull of a ship, concrete or steel tank, etc.) which remains at a temperature close to ambient.
2. Description of Prior Art
The insulating panels used in the past for such applications were made of plywood, or of plywood and of balsa wood, or of plywood boxes filled with perlite, or of plastic foam reinforced with plywood or other materials. The metal liner was then fastened to the finished wall. A common feature of all these systems is the small size of the individual elements entering in the construction of large cryogenic tank walls by these known processes.
The present invention eliminates this major drawback by providing all three required elements of a cryogenic membrane tank:
cryogenic membrane liner
impervious secondary cryogenic barrier
rigid insulation
in prefabricated panels of large dimensions, so that construction of the tank requires considerably less on-site work.